Reversing clutches with selector and pressure modulating valve

ABSTRACT

A power transmission including a forward, friction plate, modulating type friction clutch; a reverse, friction plate, modulating type clutch; a selector control valve assembly therefor, which assembly has a rotatable selector spool that during its first rotational movement acts to select the proper direction of the travel for the water craft or vehicle with which the present invention is used. Additional rotation of the selector spool in the selected direction then acts to cause a predetermined amount of modulating pressure to the selected hydraulically actuated friction type clutch. The amount of modulating pressure available selectively to either the forward or reverse clutch is determined by the amount of rotation given to the selector spool of the valve assembly and when this selected pressure has been reached, the valve assembly then reaches an equilibrium condition. An improved valve assembly having a rotatable selector spool which during its initial rotational movement acts to select either a forward or reverse, hydraulically actuated, friction plate type clutch, and then during additional rotational movement of the valve acts to provide modulating pressure for the selected clutch at the pressure determined by the rotational movement of the selector spool. After the desired amount of modulating pressure has been provided to the selected clutch, the valve assembly again reaches an equilibrium position where it is ready for the next command of the operator. A water craft having a propeller shaft capable of being driven in either rotational direction, a source of power, and a transmission driven by said source of power, said transmission including a pair of hydraulically actuated, friction plate, modulating type clutches, one for reverse and one for forward direction of the craft, and a control valve assembly for said clutches and including a rotatable selector spool. During the initial rotational movement of the selector spool, one of the clutches is selected to drive the craft in either forward or reverse directions and then continued rotational movement of the spool causes the desired amount of modulating pressure to be available to the hydraulically actuated, modulating type friction plate clutch.

United States Patent [191 Arnold 1 Aug. 14, 1973 1 1 REVERSINGCLUTCll-lES WITH SELECTOR AND PRESSURE MODULATING VALVE [75 Inventor:Bruce C. Arnold, Racine,Wis.

[73 Assignee: Twin Disc Incorporated, Racine,

Wis.

[22] Filed: May 10, 1972 [21] Appl. No.: 252,098

[52] U.S. Cl. 192/87.l9, 192/109 F, 137/625.24, 137/625.66, 74/361,91/413 Primary ExaminerBenjamin W. Wyche Attorney-James E. Nilles [57]ABSTRACT A power transmission including a forward, friction plate,modulating type friction clutch; a reverse, friction plate, modulatingtype clutch; a selector control valve assembly therefor, which assemblyhas a rotatable selector spool that during its first rotational movementacts to select the proper direction of the travel for the water craft orvehicle with which the present invention is used, Additional rotation ofthe selector spool in the selected direction then acts to cause apredetermined amount of modulating pressure to the selectedhydraulically actuated friction type clutch. The amount of modulatingpressure available selectively to either the forward or reverse clutchis determined by the amount of rotation given to the selector spool ofthe valve assembly and when this selected pressure has been reached, thevalve assembly then reaches an equilibrium condition.

An improved valve assembly having a rotatable selector spool whichduring its initial rotational movement acts to select either a forwardor reverse, hydraulically actuated, friction plate type clutch, and thenduring additional rotational movement of the valve acts to providemodulating pressure for the selected clutch at the pressure determinedby the rotational movement of the selector spool. After the desiredamount of modulating pressure has been provided to the selected clutch,the valve assembly again reaches an equilibrium position where it isready for the next command of the operator.

A water craft having a propeller shaft capable of being driven in eitherrotational direction, a source of power, and a transmission driven bysaid source of power, said transmission including a pair ofhydraulically actuated, friction plate, modulating type clutches, onefor reverse and one for forward direction of the craft, and a controlvalve assembly for said clutches and including a rotatable selectorspool. During the initial rotational movement of the selector spool, oneof the clutches is selected to drive the craft in either forward orreverse directions and then continued rotational movement of the spoolcauses the desired amount of modulating pressure to be available to thehydraulically actuated, modulating type friction plate clutch.

8 Claims, 23 Drawing Figures Patented Aug. 14,1973 I 3,752,281

14 Sheets-Sheot .l.

Patented Aug. 14; 1973 14 Sheets-Sheet 3 nmb Patented Aug. 14, 1973 14Sheets-Sheet 4 Patented Aug. 14, 1973 3,752,281

14 Sheets-Sheet 5 Patented Aug. 14, 1973 3,752,281

14 Sheets-Sheet a FIG. 13

Patented Aug. 14, 1973 14 Sheets-Sheet 9 Patented Aug. 14, 1973 14Sheets-Sheet 10 FIG. 14a

Patented Aug. 14, 1973 3,752,281

14 SheetsSheet 11 Patented Aug. 14, 1973 3,752,281

14 Sheets-Sheet 12 FIG. 16

Patented Aug. 14, 1973 14 Sheets-Sheet 13 FIG. 17

D W N 4/ AS R l 1 G NE l N 5 N m .ll F. 6 E N 9 W H 6 A m u k R 6 Q w vJ iv 5 a w M 6 H V A 6 FIIL H fig g Q G l l g wmm mm mm 8 &LB O RQ O D CC F M R Patented Aug. 14, 1973 14 Sheets-Sheet 14.

ZOFUMEQ QK MOL mml mp1 mmbwmmmm 02533002 ZEbmZ omw mbw oom lSd BHHSSBEHREVERSING CLUTCIIES WITH SELECTOR AND PRESSURE MODULATING VALVEBACKGROUND OF THE INVENTION The present invention relates to powertransmission and to control valve assemblies therefor and findsparticular utility in driving a load where a centrifugal valve operatedclutch is used and the power requirement is proportional to the cube ofthe speed, for example, as in a water craft having a propeller shaftthat is to be driven in either rotational direction. While the inventionfinds particular utility when used with such water craft, other uses ofthe present invention are possible, such as for example with a torqueconverter, or other devices.

One example of a prior art transmission of the hydraulically actuated,friction clutch type, which clutches have centrifugal valves to regulatetheir output speed, is shown in the US. Pat. No. 3,6l3,469, issued Oct.19, I971 to McRoberts and Arnold, and which is entitled PowerTransmission of the I-Iydraulically Actuated, Friction Clutch Type."That patent utilized an electrical circuit including solenoids andswitches in the controlling mechanism.

SUMMARY OF THE INVENTION The present invention provides a powertransmission including a pair of hydraulically actuated, friction platetype, modulating type clutches, one for effecting reverse direction andone for effecting forward direction of the vehicle or craft with whichthe invention is used, having an output shaft which is to be driven ineither rotational direction, and a control valve assembly for selectingthe desired clutch which is to be engaged and then causing the desiredamount of fluid pressure to be available at the selected clutch so thatthe vehicle, craft, or other load is driven at a constant speed in theselected direction.

The invention is also directed to an improved-control valve assembly fortransmission of the above type wherein the assembly includes a rotatableselector spool which is under the influence of the operator and which,during its first or initial rotational movement acts to direct pressurefluid to either a forward or reverse, hydraulically actuated frictionplate, modulating type clutch. After the desired clutch has beenselected to thereby provide the proper direction of movement for theload, further rotational movement of the selector spool in therotational direction selected, then acts to provide the desired amountof pressure fluid to the clutch so that the modulating clutch outputspeed remians constant. After the desired speed for the output of theclutch has been selected, the valve assembly stays to a balancedcondition.

Another aspect of the invention relates to providing a powertransmission and control valve assembly as above mentioned for use witha water craft having a propeller that is to be driven in eitherrotational direction.

These and other objects and advantages of the present invention willappear hereinafter as this disclosure progresses, reference being had tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is generally a longitudinal,cross sectional view through the selector valve assembly made inaccordance with the present invention, certain parts shown as beingbroken away or removed for clarity;

FIG. 2 is a view of the valve assembly shown in FIG. 1 and takengenerally along the line 2-2 in FIG. 1, but with certain parts beingshown as broken away, in section, or removed for the sake of clarity inthe drawings;

FIG. 2a is an elevational view of the axially shiftable valve spoolshown in FIG. 2;

FIG. 3 is an elevational view of the selector spool asshown in FIG. 1;

FIG. 4 is another view of the selector spool, as shown in FIG. 2;

FIG. 4a is a view of a portion of the selector spool shown in FIG. 4 butshowing the selector spool when rotated to a different position so as toblock its orificing hole;

FIG. 4b is a view similar to FIG. 4a, but showing the control pistonwhen it has shifted so as to shift the valve spool and also againuncover the orificing hole to create a balanced condition;

FIG. 5 is a fragmentary, cross sectional view taken generally along theline 5-5 in FIG. 1;

FIG. 6 is a transverse cross sectional view taken along line 6-6 in FIG.1;

FIG. 7 is a transverse, cross sectional view through the sump pressurechamber and taken along 7-7 in FIG. 1;

FIG. 8 is a transverse, cross sectional view through the modulatingpressure chamber and taken along line 8-8 in FIG. 1; I

FIG. 9 is a transverse, cross sectional view through the high pressuresupply chamber and taken along line 9-9 in FIG. 1;

FIG. 10 is a transverse, cross sectional view taken generally along theline 10-10 in either FIGS. 1 or 2;

FIG. 11 is a transverse, cross sectional view taken generally along theline 11-11 in FIG. 2;

FIG. 12 is a fragmentary, cross sectional view taken generally along theline 12-12 in FIG. 2;

FIG. 13 is a longitudinal, cross sectional view taken along line 13-13of FIG. 1;

FIG. 14 is a generally schematic, elevational view of a water craftembodying the present invention;

FIG. 14a is an end elevational view of a power transmission embodyingthe selector valve assembly shown in the other figures and the forwardand reverse shafts and their gears, the view being taken generally alongline l4a-14a in FIG. 14, but on an enlarged scale;

FIG. 15 is a longitudinal cross sectional view of the forward clutch andthe power input shaft, the view being taken generally along the line15-15 in 'FIG. 140, but on an enlarged scale, certain parts being shownas further broken away for the sake of clarity;

FIG. 15a is an enlarged fragmentary view of the centrifugal valve shownin FIG. 15;

FIG. 16 is a fragmentary and longitudinal, cross sectional view of thereverse clutch and its shaft, the view being taken generally along theline 16-16 in FIG. 14a, but on an enlarged sclae;

FIG. 17 is a generally schematic hydraulic circuit diagram of thecircuit used with the present invention; and

FIG. 18 is a graph showing the direction of movement of the vehicle orcraft to be driven by the present invention as plotted against thepressure available to engage the clutches shown in FIGS. 15 and 16.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring generally to FIGS. 14and 14a, the power transmission PT provided by the present invention isshown in a water craft WC where it finds particular utility and isdriven from a power source such as an internal combustion engine E. Thetransmission includes a main housing H in which is rotatably mounted apower input shaft 1 which is driven from the engine, through thecoupling 2 splined at 3 to the shaft 1.

Shaft 1 (FIG. 15) is suitably journalled by antifriction bearingassemblies 4 and 5 mounted in the housing and has a pinion 6 rotatablymounted thereon. A gear 7 is fixed on shaft 1 and the shaft 1 also has adiametrically enlarged annular portion 8 having external splines 9 onwhich are mounted the series of conventional friction plates 10 whichrotate with the shaft 1. A clutch drum or friction plate carrier 13 hasan end wall portion 13a rotatably journalled on shaft 1 and the carrieralso includes an axially spaced end wall portion 13b that is splined at14 to the hub of pinion 6. Portion 13b is rotatably journalled in thehousing by the antifriction bearing assembly 15. A clutch clamp-uppiston 17 is slideably mounted on the axially extending hub 18 ofcarrier portion 130, and this piston can shift axially, between clutchengaged and disengaged positions, due to fluid pressurization of anactuating chamber 20 formed between carrier portion 13a and the piston17.

Pressure fluid is introduced to the expansible pressure chamber 20 viafluid passages 21 which is located in shaft 1 and through a centrifugalvalve 40 (to be later described) in the portion 13a.

A series of friction plates 24 are mounted on the internal splines 25formed in the carrier 13, and these plates 24 are interleaved with theshaft carried plates 10 and all of the plates are axially shfitableslightly so as to cause engagement and disengagement between the shaft 1and gear 6 in the known manner. Bolt means 26 are located between endwalls portions 13a: and 13b and the piston 17 is slidingly and guidinglymounted on these circumferentially spaced bolt means. Furthermore, theseinterleaved plates can be made to slippingly engage one another to anydegree, that is the clutch can be made to modulate to any degree so asto provide slipping engagement, thereby providing varying degrees ofdriving ability between the shaft 1 and gear 6.

I The amount of clutch clamp up or engagement is provided by acentrifugally operated fluid valve 40, previously referred to, which islocated in the carrier 13. Pressure fluid is fed to this valve 40through the passage 21 in shaft 1 extending through the member 13 (FIG.15) to the outer end of a radially shiftable spool 42 of the valve 40. Apassage 42a in spool 42 and an alignable passage 43 in member 13 canplace the valve chamber 44 in spool 42 in fluid communication with theclutch actuating chamber 20. An orifice 45 is provided for the valve tocontinually bleed fluid therefrom. A valve of this type is shown in the(1.8. Pat., to I-Iilpert, No. 3,352,395, which issued Nov. 14, 1967 andentitled Friction Clutch having Centrifugally Operated Valve Means," andif further details concerning the valves construction and operation aredeemed to be either necessary or desirable, reference may be had to thatpatent. Such a valve is also shown in the US. Pat. No. 3,613,469 whichissued Oct. 19, 1971 and in which I am a co-inventor, and which,together with the said Hilpert Patent, have been assigned to an assigneecommon with the present application. It is believed to be sufficient tosay, in connection with the valve 40, that as the carrier 13 rotates,centrifugal force acts to bias the spool 42 in a radial, outwarddirection, against the fluid pressure on the radial outer end of thevalve which comes from passage 21. As rotational speed increases above apredetermined minimum, and spool 42 shifts radially outwardly to causepassage 43 to close and thereby cut off further flow to the clutchactuating chamber 20; this action causes the clutch plates to slip,thereby reducing output speed of the clutch. Conversely, when therotational speed falls below a predetermined minimum, the spool 42 isshifted radially inwardly by the pressure, thereby exposing passage 43to more fluid pressure, thus providing additional clampup force to thepiston 17 and consequently to the clutch plates against which it bears,thereby increasing the clutch output speed. In this manner, the outputspeed of the friction plate clutch CF and the output shaft is heldconstant.

Referring now to FIG. 16, a reverse shaft is journailed for rotation bysuitable anti-friction bearing assemblies 51 and 52 and the constructionof the reverse clutch CR, and the centrifugal valve 53, is similar tothat described in connection with FIG. 15, similar parts beingcorrespondingly numbered with the addition of the suffix r. The shaft 50also has a pinion 54 formed thereon. The shaft 50 has a gear 55 fixedthereon. Gear 7 of shaft 1 is in constant mesh with gear 55 of shaft 50.

The relationship between the forward clutch CF and the reverse clutch CRand their corresponding shafts and gears is as follows. .A power outputgear 57 is fixed to the power output shaft 58 (FIGS. 15 and 14a)rotatably journalled in the housing, and this gear 57 is in constantmesh with both pinion 6 on shaft 1 and pinion 54 of shaft 50, asindicated in FIG. 140. An attaching flange 59 is fixed to the end ofshaft 58 and a propeller shaft 60 (FIG. 14) is attached to this flangeIn this manner, either the forward clutch CF can be engaged, and clutchCR released, to provide forward direction to the vehicle or craft, orthe reverse clutch CR is engaged and clutch CF is released to providethe reverse direction to the vehicle or craft, as follows.

When the clutch CF is engaged, the clutch CR is disengaged and powerflows through shaft 1, carrier 13, pinion 6, and gear 57 to the outputshaft 58 (FIG. 14a) of the transmission. When a reverse direction isdesired, the clutch CF is released and clutch CR is engaged, therebycausing the power flow to be through shaft 1, gear 7 of shaft 1, gear 55of shaft 50, through the clutch plate carrier 13r, pinion 54 and thenthrough the meshing gear 57 to the output shaft 58.

Referring to FIGS. 14a and 17, the general organization of the componentparts will now be referred to. A sump S is located in the bottom of thetransmission housing H and fluid is sucked therefrom via conduit 61 bythe fluid pump 62 after first passing through a screen 63 ofconventional character. The fluid then passes through a filter 64through conduit 65 to a high pressure regulating valve 66. This valve 66determines the amount of fluid pressure which will ultimately bedirected via passage 67 (FIGS. 2, 10 and 17), through the modulatingvalve MV and the conduit 68 to the centrifugal valve 40r andconsequently the actuating chamber of the reverse clutch CR oralternately via conduit 69 to the centrifugal valve 40 of the forwardclutch CR.

Some fluid discharged from regulating valve 66 is also used to cool theforward and reverse clutches and also lubricate the variousanti-friction bearings and gears and this fluid is conducted from thehigh pressure valve 66 via line 70 to the various said component parts,as indicated schematically in FIG. 17.

Reference has been made to the fact that a certain amount of highpressure fluid is directed to the modulating valve assembly MV and thedescription of this valve and its operation will now be described.

The general construction and arrangement of this valve MV is such thatit has a rotatable selector spool 72 which is shown clearly in FIGS. 1,2, 3, and 4, among others. The valve 40 also has an axially shiftablepressure control piston 77 and an axially shiftable, modulating valvespool 79, to be described. The valve MV is actuated by rotation of thespool 72 and this rotation is done manually and for example, can beaccomplished by causing a sprocket 73, fixed on the outer end of thespool, to be rotated by the operator of the vehicle or craft. Initialrotation of the spool 72 from a neutral position, which neutral positionis shown in FIGS. 1, 2, 3, 4, 5 and 6, causes selection of the directionof vehicle movement, depending on which direction of rotation of thevalve. This initial movement is, for example, in the amount ofapproximately degrees in either reverse or forward directions, and thisvalve movement is further indicatd in the graph of FIG. 18. After thisinitial rotational movement of the valve spool in either direction,continued rotation in the selected direction causes a rise or increasingmodulation of the fluid pressure which is delivered to the selectedclutch CR or CR. This modulating pressure rise is shown in FIG. 18 asthe inclined line in either direction. Then, when a predeterminedpressure has been reached, say for example as at point 120, the clutchoutput speed will remain constant.

The more specific operation of the modulating valve and its orificebalancing feature will now be referred to The valve MV includes a valvehousing or body 75 having an axial bore 71 in which the selector spool72 is rotatable. The axially shiftable piston 77 ismounted within bore78 of the body 75 and an axially shiftable spool 79 mounted in bore 76having an enlarged end 79a is also mounted in the body.

The spool 79 (FIG. includes land portions 790, and 79d and anintermediate, diametrically reduced portion 7%. The valve body 75 alsoincludes a high pressure chamber 80, a modulating pressure chamber 81and a sump pressure chamber 82, all of which are communicable with thevalve spool 79. A light spring 83 is located in the end portion 84 ofthe bore 76 and tends to urge the spool 79 to the left, as viewed inFIG. 1. When the valve spool 79 is shifted to the left (FIG. 1), thesump chamber 82 acts to vent the modulating pressure when that pressurebecomes excessive.

High pressure fluid is introduced into the valve housing through passage67 (FIGS. 2 and 10) and then through an axial passage 67a to the highpressure chamber 80. Thus, high pressure is always available in chamber80. High pressure fluid which is thus introduced into chamber 80 isthrottled at the small annular groove 90 formed at the juncture of theland 7% of the valve spool and the bore 76. This high pressure isthereby reduced into modulating pressure in chamber 81.

Referring to FIGS. 2 and 12, a certain amount of high pressure fluid isalso directed from the axial passage 67a through a cored passage 69which in turn communicates with another axially extending passage 67b(FIGS. 2, l1 and 12). The passage 67b then communicates with atransverse passage 67c (FIG. 11) containing an orifice 67d through whichthe fluid pressure is throttled, causing a pressure drop. The pressurefluid then passes through a transverse hole 72c in the spool stem 720.

As shown in FIG. 2, a fluid passage 85 connects the modulating pressurechamber 81 with the end portion bore 84 at the end of the spool, andconsequently, modulating pressure is thus directed to the end of thespool for urging it to the left. A pair of springs 87 and 88 (FIG. 1) ofdifferent strengths, act between the piston 77 and the enlarged end 79aof the spool 79 and urge the spool 79 to the right hand position (asviewed in FIG. 1), and against the action of the modulating pressure andthe spring 83 at the opposite end of the spool 79.

Modulating pressure is also conducted from chamber 81 through the rightangle passage 92 (FIG. 1) through a cross port 91 in stem 72a and thenthrough the central and axially extending passage 93 to the radialpassage 94 (FIGS. 1 and 6) in the diametrically enlarged portion 72b ofthe selector spool 72, which enlarged portion 72b is rotatable in thelarge bore 96 formed in the housing 75. Also formed in the housing, asshown clearly in FIG. 6, is a passage 100 that conducts the modulatingpressure as will appear, to and from the forward clutch CF. Anotherpassage 101 which, depending on the rotational position of the selectorspool 72, conducts the modulating pressure to and from the reverseclutch CR.

Low or sump pressure is also conducted to each axial I side of theenlarged portion 72b of the selector spool so as to hydraulicallybalance the selector spool, thus faciliating its easy rotation. Thissump pressure is located in an annular space 102 at the right side(FIG. 1) of the enlarged portion 72b, and sump pressure is conducted tothe space 103 on the left side of the enlarged portion 72b via the axialports 104a and 104b (FIGS. 1, 5 and 6) which extend through the enlargedportion 72b.

The passage 104a or 104b also serve to dump or exhaust that particularclutch which is not being engaged. For example, in the position shown inFIG. 6, both clutches are being vented to sump because the transmissionis in neutral. When the spool 72 is rotated (as indicated by thecurvilinear arrow) to permit modulating pressure to flow to the forwardclutch passage 100, then port 104a acts to vent the reverse clutchpassage 101 to the sump via spaces 102 and 103 (FIG. 1), and passages105, 106 (FIG. 10).

As shown in FIG. 5, a spring loaded plunger 112 selectively engageseither the neutral detent 108, the forward detent 111, or the reversedetent 110.

With the above construction, initial rotation of the selector spool 72causes modulating fluid pressure to be selectively directed to either ofthe clutches CF or CR.

The pressure control piston 77 (FIGS. 1, 2, 3 and 4) previously referredto has an elongated and diametrically smaller sleeve 77b which is-cutaway, as clearly indicated in FIGS. 3, 4, 4a and 4b, to form an inclinedor tapered surface 77c which defines a V-shaped opening 77d. ThisV-shaped opening is symmetrical about a longitudinal centerline whenviewed in FIG. 4 and increases in depth from right to left when viewedin FIG. 3.

The transverse hole 72c of the spool stem 72a communicates with thecentral axial passage 72d of the spool 72. Passage 72d is defined ateither end by the sealing balls 74 and 74a. Furthermore, the spool 72has a radial port 72e. High pressure fluid is thus conducted throughpassage 67a, 67b, 67c, orifice 67d, chamber 107, passage 72c, radialport 72e and when port 72e is open, to the sump pressure area at theright side of piston 77. This hole or port 72e acts as an orifice, aswill appear, and can be either open, fully closed, or partially closeddepending both on the rotational position of the selector spool 72 aswell as the axial position of the piston 77.

The annular chamber 107 which is formed in the housing 75 adjacent thepiston 77 permits high pressure fluid to act against the left side(FIG. 1) of the piston 77, thereby urging the latter to the right andagainst the bias of the springs 87 and 88, and also against the actionof the valve spool 79.

The operation of the above control valve assembly and transmission is asfollows.

High pressure fluid is always available at the high pressure chamber 80and when the valve is in the equilibrium position shown in FIGS. 1, 2, 3and 4, this high pressure fluid is throttled through the groove 90 (FIG.1 and into the modulating pressure chamber 81. At the same time, highpressure fluid flows through the cored passage 69 (FIGS. 2 and 4b), andinto passage 67b, 67c, through orifice 67d and as the fluid passesthrough the orifice 67d its pressure drops. Pressure fluid is thusavailable in the chamber 107 to act on the end of the control piston 77.However, as long as the orificing hole 72e in the selector spool stem isopen, this pressure simply flows through orifice 72e to the sump area,and consequently the control piston 77 does not shift to the right.

Referring again to the modulating pressure which is then in chamber 81,this pressure is then conducted in an axial direction through thepassage 92 and then radially intothecenter axial passage 93 of theselector spool where it then is delivered to the radial passage 94(FIG.6). If the selector spool is in the neutral position shown, noaction occurs. However, if the selector spool is initially rotated ineither direction, the modulating pressure, designated MP in FIG. 6 isavailable to either the passage 100, which is in communication with theforward clutch CF or alternatively, to the passage 101 which is incommunication with the reverse clutch CR. Thus, initial rotation of theselector spool actually selects the direction of rotation of the outputof the transmission.

Reference will now be made to the action of the selector spool indirecting a certain amount of modulating pressure to the selectedclutch. Referring also to FIGS. 3, 4, 4a and 4b, FIG. 4 shows theposition of the selector spool in the neutral position and FIG. 4a showsthe selector spool stern when it has been rotated as above described,which has moved the orificing hole 72e to a position where it is blockedor covered by the sleeve 77b of the piston. This blocking of theorificing hole 72e causes a build up of pressure in the chamber 107behind the piston 77, thereby urging the piston 77 to the right as shownin FIG. 4b. When thepiston has moved axially sufficiently as shown inFIG. 4b, the hole 72e is again uncovered. In moving to the right, thepiston through the action of the springs 87 and 88 causes the valvespool 79 to shift to the right (FIG. 4b) against the modulating pressurein chamber 84 and also against the action of the spring 83 in thechamber 84. This shifting of the spool 79 causes a greater openingbetween the high pressure chamber and the modulating pressure chamber81, thus causing more pressure fluid to flow into the modulating chamberas indicated by the arrow in FIG. 4b. This increased pressure then ofcourse is directed to the selected clutch via the passages 92, 93, 94and either or 101.

For example, referring to FIG. 18, assume the position to which theselector spool has been rotated as shown in FIGS. 4a and 4b, is suchthat an amount of modulating pressure is provided to the clutch asrepresented by the point on the chart, and also assuming that theforward clutch CF has been selected. The pressure represented at point120 on the chart in FIG. 18 represents one output speed of the clutch,that is to say it represents the pressure that is imposed on theradially outer end of the control valve 40 of the particular clutchselected. It will be seen that any degree of modulating pressure can beselected for either the clutch, that is to say, any constant outputspeed of the clutch may be selected by the selector spool rotationalmovement.

Thus, the control piston 77 moves axially to follow up to a point wherethe hole 72e is again exposed, and this amount of follow-up movement isdependent on how much rotational movement was imparted to the selectorspool.

The piston will hold its selected axial position, as determined by theamount of rotation of the selector spool, whenever the pressure dropacross the orifice 67d is equal to the pressure drop through hole 72e.

The springs 87 and 88 act together to prvide a reference force, that is,a force that represents the amount of working pressure desired. Thisspring force is balanced by the modulating pressure acting on the end ofthe piston 77. Thus, the amount of rotation of the selector spool 72determines the amount of modulating pressure admitted to the clutch andconseuqentiy determines the output speed of the transmission.

I claim:

l. A power transmission comprising, a hydraulically actuated forwardclutch of the modulatable friction plate type, a hydraulically actuatedreverse clutch of the modulatable friction plate type, and a hydraulicvalve assembly for controlling the selection of engagement of either ofsaid clutches and also for controlling the modulation of the selectedclutch, said valve assembly comprising; a valve body and a rotatableselector spool in said body and having passage means for directing fluidpressure selectively to either of said clutches when said selector spoolis initially rotated in a corresponding direction from a neutralposition, said selector spool having a fluid orificing hole, a fluidcontrol piston axially shiftable on said selector spool and having agenerally V-shaped opening in its periphery which is registerable withsaid orificing hole, spring means for biasing said piston toward oneaxial position, a hydraulic valve spool axially shiftable in said bodyand biased by said spring means away from said piston, a high pressurefluid passage means and also modulating pressure fluid passage means insaid body both communicable with said hydraulic valve spool, wherebyhigh pressure is throttled into said modulating pressure fluid passagemeans, said modulating pressure fluid passage means also being incommunication with the end of said valve spool which is remote from saidspring means to thereby urge said valve spool against said spring meansand towards said piston to additionally bias the latter, said modulatingpressure fluid passage means also in communication with said selectorspool passage means, said hydraulically actuated clutches having conduitmeans communicating with said passage means in said selector spool,whereby modulating pressure is delivered selectively to said clutches,said high pressure fluid passage means also communicating with the sideof said piston remote from said spring means to thereby bias said pistontowards said valve spool to thereby also bias the latter through saidspring means to a position which permits an increase of pressure fluidfrom said high pressure fluid passage means to said modulating pressurefluid passage means, the cooperative arrangement between said generallyV-shaped opening on said piston and said hole in the said selector spoolis such that when said selector spool is rotated in either directionfrom neutral, said hole is blocked, and said piston is then shiftedaxially by pressure fluid on said piston side to uncover said hole andmodulating pressure fluid is directed to said engaged clutch at apressure dependent on the amount of rotation of said selector spool,thereby to cause clutch engagement.

2. The transmission set forth in claim 1 further characterized in thatsaid selector spool includes a central stem with an axial passagetherein and said orificing hole is located in said stem and in fluidcommunication with said axial passage, and further characterized in thatsaid control piston includes a sleeve in which said generally V-shapedopening is located.

3. A power transmission comprising a power input shaft, a power outputshaft, intermeshing gear means between said shafts, a hydraulicallyactuated forward clutch of the modulatable friction plate type and ahydraulically actuated reverse clutch of the modulatable friction platetype connectable with said gear means,

and a hydraulic valve assembly for controlling the selection ofengagement of either of said clutches and also for controlling themodulation of the selected clutch, said valve assembly comprising: avalve body and a rotatable selector spool in said body and havingpassage means for directing fluid pressure selectively to either of saidclutches when said selector spool is initially rotated in acorresponding direction from a neutral position, said selector spoolhaving a central stem with an axial passage therein and a hole in saidstem and in communication with said axial passage, a fluid controlpiston axially shiftable on said selector spool and having a sleevedefining a generally V-shaped opening in its periphery which isregisterable with the hole in said selector spool stern, spring meansfor biasing said piston toward one axial position, a hydraulic valvespool axially shiftable in said body and biased by said spring meansaway from said piston, a high pressure fluid passage means andmodulating pressure fluid passage means in said body and communicablewith said hydraulic valve spool, whereby high pressure is throttled asmodulating pressure into said modulating pressure fluid passage means,said modulating pressure fluid passage means also being in communicationwith the end of said valve spool which is remote from said spring meansto thereby urge said valve spool which is remote from said spring meansto thereby urge said valve spool against said spring means and towardssaid piston to additionally bias the latter, said modulating pressurefluid passage means also in communication with said selector spoolpassage means, said hydraulically actuated clutches having conduit meanscommunicating with said passage means in said selector spool, wherebymodulating pressure is delivered selectively to said clutches, said highpressure fluid passage means also communicating with the side of saidpiston remote from said spring means to thereby bias said piston and itssaid spring means to a position which permits an increase of pressurefluid from said high pressure fluid passage means to said modulatingpressure fluid passage means, the arrangement between said generallyV-shaped opening on said piston sleeve and said hole in the saidselector spool stem is such that when said selector spool is rotated ineither direction from neutral, said hole is blocked until said piston isshifted axially to uncover said hole and modulating pressure fluid isdirected to said engaged clutch in an amount dependent on the amount ofrotation of said selector spool to cause clutch engagement andconsequent rotation of said output shaft in either direction of rotationand at a predetermined constant speed.

4. A fluid pressure control valve assembly comprising: a valve body anda rotatable selector spool in said body and having passage means fordirecting fluid pressure selectively to either of two loads when saidselector spool is initially rotated from a neutral position, saidselector spool having a fluid orificing hole, a fluid control pistonaxially shiftable on said selector spool and having a generally V-shapedopening in its periphery which is registerable with said orificing hole,spring means for biasing said piston toward one axial position, ahydraulic valve spool axially shiftable in said body and biased by saidspring means away from said piston, a high pressure fluid passage meansand modulating pressure fluid passage means in said body andcommunicable with said hydraulic valve spool, whereby high pressure isthrottled into said modulating pressure fluid passage means, saidmodulating pressure fluid passage means also being in communication withthe end of said valve spool which is remote from said spring means tothereby urge said valve spool against said spring means and towards saidpiston to additionally bias the latter, said modulating pressure fluidpassage means also in communication with said selector spool passagemeans, said passage means in said selector spool being communicable withsaid loads for conducting modulating pressure selectively to said loads,said high pressure fluid passage means also communicating with the sideof said piston remote from said spring means to thereby bias said pistontowards said valve spool to thereby bias the latter through said springmeans to a position which permits an increase of pressure fluid fromsaid high pressure fluid passage means to said modulating pressure fluidpassage means, the arrangement between said generally V-shaped openingon said piston and said hole in the said spool in such that when saidselector spool is rotated in either direction from neutral, said hole isblocked until said piston is shifted axially to uncover said hole andmodulating pressure fluid can be directed to said loads in an amountdependent on the amount of rotation of said selector spool.

1. A power transmission comprising, a hydraulically actuated forwardclutch of the modulatable friction plate type, a hydraulically actuatedreverse clutch of the modulatable friction plate type, and a hydraulicvalve assembly for controlling the selection of engagement of either ofsaid clutches and also for controlling the modulation of the selectedclutch, said valve assembly comprising; a valve body and a rotatableselector spool in said body and having passage means for directing fluidpressure selectively to either of said clutches when said selector spoolis initially rotated in a corresponding direction from a neutralposition, said selector spool having a fluid orificing hole, a fluidcontrol piston axially shiftable on said selector spool and having agenerally V-shaped opening in its periphery which is registerable withsaid orificing hole, spring means for biasing said piston toward oneaxial position, a hydraulic valve spool axially shiftable in said bodyand biased by said spring means away from said piston, a high pressurefluid passage means and also modulating pressure fluid passage means insaid body both communicable with said hydraulic valve spool, wherebyhigh pressure is throttled into said modulating pressure fluid passagemeans, said modulating pressure fluid passage means also being incommunication with the end of said valve spool which is remote from saidspring means to thereby urge said valve spool against said spring meansand towards said piston to additionally bias the latter, said modulatingpressure fluid passage means also in communication with said selectorspool passage means, said hydraulically actuated clutches having conduitmeans communicating with said passage means in said selector spool,whereby modulating pressure is delivered selectively to said clutches,said high pressure fluid passage means also communicating with the sideof said piston remote from said spring means to thereby bias said pistontowards said valve spool to thereby also bias the latter through saidspring means to a position which permits an increase of pressure fluidfrom said high pressure fluid passage means to said modulating pressurefluid passage means, the cooperative arrangement between said generallyV-shaped opening on said piston and said hole in the said selector spoolis such that when said selector sPool is rotated in either directionfrom neutral, said hole is blocked, and said piston is then shiftedaxially by pressure fluid on said piston side to uncover said hole andmodulating pressure fluid is directed to said engaged clutch at apressure dependent on the amount of rotation of said selector spool,thereby to cause clutch engagement.
 2. The transmission set forth inclaim 1 further characterized in that said selector spool includes acentral stem with an axial passage therein and said orificing hole islocated in said stem and in fluid communication with said axial passage,and further characterized in that said control piston includes a sleevein which said generally V-shaped opening is located.
 3. A powertransmission comprising a power input shaft, a power output shaft,intermeshing gear means between said shafts, a hydraulically actuatedforward clutch of the modulatable friction plate type and ahydraulically actuated reverse clutch of the modulatable friction platetype connectable with said gear means, and a hydraulic valve assemblyfor controlling the selection of engagement of either of said clutchesand also for controlling the modulation of the selected clutch, saidvalve assembly comprising: a valve body and a rotatable selector spoolin said body and having passage means for directing fluid pressureselectively to either of said clutches when said selector spool isinitially rotated in a corresponding direction from a neutral position,said selector spool having a central stem with an axial passage thereinand a hole in said stem and in communication with said axial passage, afluid control piston axially shiftable on said selector spool and havinga sleeve defining a generally V-shaped opening in its periphery which isregisterable with the hole in said selector spool stem, spring means forbiasing said piston toward one axial position, a hydraulic valve spoolaxially shiftable in said body and biased by said spring means away fromsaid piston, a high pressure fluid passage means and modulating pressurefluid passage means in said body and communicable with said hydraulicvalve spool, whereby high pressure is throttled as modulating pressureinto said modulating pressure fluid passage means, said modulatingpressure fluid passage means also being in communication with the end ofsaid valve spool which is remote from said spring means to thereby urgesaid valve spool which is remote from said spring means to thereby urgesaid valve spool against said spring means and towards said piston toadditionally bias the latter, said modulating pressure fluid passagemeans also in communication with said selector spool passage means, saidhydraulically actuated clutches having conduit means communicating withsaid passage means in said selector spool, whereby modulating pressureis delivered selectively to said clutches, said high pressure fluidpassage means also communicating with the side of said piston remotefrom said spring means to thereby bias said piston and its said springmeans to a position which permits an increase of pressure fluid fromsaid high pressure fluid passage means to said modulating pressure fluidpassage means, the arrangement between said generally V-shaped openingon said piston sleeve and said hole in the said selector spool stem issuch that when said selector spool is rotated in either direction fromneutral, said hole is blocked until said piston is shifted axially touncover said hole and modulating pressure fluid is directed to saidengaged clutch in an amount dependent on the amount of rotation of saidselector spool to cause clutch engagement and consequent rotation ofsaid output shaft in either direction of rotation and at a predeterminedconstant speed.
 4. A fluid pressure control valve assembly comprising: avalve body and a rotatable selector spool in said body and havingpassage means for directing fluid pressure selectively to either of twoloads when said selector spool is initially rotated from a neutralposition, said selector spool having a fluid orificing hole, a fluidcontrol piston axially shiftable on said selector spool and having agenerally V-shaped opening in its periphery which is registerable withsaid orificing hole, spring means for biasing said piston toward oneaxial position, a hydraulic valve spool axially shiftable in said bodyand biased by said spring means away from said piston, a high pressurefluid passage means and modulating pressure fluid passage means in saidbody and communicable with said hydraulic valve spool, whereby highpressure is throttled into said modulating pressure fluid passage means,said modulating pressure fluid passage means also being in communicationwith the end of said valve spool which is remote from said spring meansto thereby urge said valve spool against said spring means and towardssaid piston to additionally bias the latter, said modulating pressurefluid passage means also in communication with said selector spoolpassage means, said passage means in said selector spool beingcommunicable with said loads for conducting modulating pressureselectively to said loads, said high pressure fluid passage means alsocommunicating with the side of said piston remote from said spring meansto thereby bias said piston towards said valve spool to thereby bias thelatter through said spring means to a position which permits an increaseof pressure fluid from said high pressure fluid passage means to saidmodulating pressure fluid passage means, the arrangement between saidgenerally V-shaped opening on said piston and said hole in the saidspool in such that when said selector spool is rotated in eitherdirection from neutral, said hole is blocked until said piston isshifted axially to uncover said hole and modulating pressure fluid canbe directed to said loads in an amount dependent on the amount ofrotation of said selector spool.
 5. A control valve assembly comprising;a valve body and a rotatable selector spool in said body and havingpassage means for directing fluid pressure selectively to either of twoloads when said selector spool is initially rotated in a correspondingdirection from a neutral position, said selector spool also having ahole in its periphery, a fluid control piston member axially shiftableon said selector spool and having a generally V-shaped opening in itsperiphery which is registerable with the hole in said selector spool,means for biasing said piston member toward one axial position, ahydraulic valve spool axially shiftable in said body and biased by saidpiston member biasing means away from said piston member, a highpressure fluid passage means and modulating pressure fluid passage meansin said body and communicable with said hydraulic valve spool and witheach other via said valve spool, said modulating pressure fluid passagemeans also being in communication with the end of said valve spool whichis remote from said spring means to thereby urge said valve spoolagainst said piston member biasing means and towards said piston meansto additionally bias the latter, said modulating pressure fluid passagemeans also in communication with said selector spool passage means, saidhigh pressure fluid passage means also communicating with the side ofsaid piston means remote from said piston member biasing means tothereby bias said piston means towards said valve spool to thereby biasthe latter through said piston member biasing means to a position whichpermits an increase of pressure fluid from said high pressure passagemeans to said modulating pressure passage means, the arrangement betweensaid generally V-shaped opening on said piston means and said hole insaid selector spool is such that when said sleector spool is rotated ineither direction from neutral, said hole is blocked until said pistonmeans is shifted axially to uncover said hole and modulating pressurefluid can be directed to a selected load via said rotatable spoolpassage means in an amount dependent on tHe amount of rotation of saidselector spool.
 6. A control valve assembly for controlling theselection and amount of modulation and a pair of hydraulically actuated,modulatable friction plate clutches, said assembly comprising: a valvebody and a rotatable selector spool in said body and having passagemeans for directing fluid pressure selectively to either of saidclutches when said selector spool is initially rotated in acorresponding direction from a neutral position, said selector spoolhaving a central stem with an axial passage therein and a hole in saidstem and in communication wtih said axial passage, a fluid controlpiston axially shiftable on said selector spool and having a sleevedefining a generally V-shaped opening in its periphery which isregisterable with the hole in said selector spool stem, spring means forbiasing said piston toward one axial position, a hydraulic valve spoolaxially shiftable in said body and biased by said spring means away fromsaid piston, a high pressure fluid passage means and modulating pressurefluid passage means in said body and communicable with said hydraulicvalve spool, whereby high pressure is throttled as modulating pressureinto said modulating pressure fluid passage means, said modulatingpressure fluid passage means also being in communication with the end ofsaid valve spool which is remote from said spring means to thereby urgesaid valve spool against said spring means and towards said piston toadditionally bias the latter, said modulating pressure fluid passagemeans also in communication with said selector spool passage means, saidpassage means in said selector spool being communicable with saidclutches, whereby modulating pressure can be delivered selectively tosaid clutches, said high pressure fluid passage means also communicatingwith the side of said piston remote from said spring means to therebybias said piston and its sleeve towards said valve spool to thereby biasthe latter through said spring means to a position which permits anincrease of pressure fluid from said high pressure fluid passage meansto said modulating pressure fluid passage means, the arrangement betweensaid generally V-shaped opening on said piston sleeve and said hole inthe said spool stem is such that when said selector spool is rotated ineither direction from neutral, said hole is blocked until said piston isshifted axially to uncover said hole and modulating pressure fluid canbe directed to said engaged clutch in an amount dependent on the amountof rotation of said selector spool.
 7. In combination with a water crafthaving an engine, a power transmission driven by said engine andincluding a hydraulically actuated forward clutch of the modulatablefriction plate type and a hydraulically actuated reverse clutch of themodulatable friction plate type, and a propeller shaft driven in eitherrotational direction by said transmission, and a hydraulic valveassembly for controlling the selection of engagement of either of saidclutches and also for controlling the modulation of the selected clutch,said valve assembly comprising: a valve body and a rotatable selectorspool in said body and having passage means for directing fluid pressureselectively to either of said clutches when said selector spool isinitially rotated in a corresponding direction from a neutral position,said selector spool having a fluid orificing hole, a fluid controlpiston axially shiftable on said selector spool and having a generallyV-shaped opening in its periphery which is registerable with saidorificing hole, spring means for biasing said piston toward one axialposition, a hydraulic valve spool axially shiftable in said body andbiased by said spring means away from said piston, a high pressure fluidpassage means and modulating pressure fluid passage means in said bodyand communicable with said hydraulic valve spool, whereby high pressureis throttled into said modulating pressure fluid passage means, saidmodulating presSure fluid passage means also being in communication withthe end of said valve spool which is remote from said spring means tothereby urge said valve spool against said spring means and towards saidpiston to additionally bias the latter, said modulating pressure fluidpassage means also in communication with said selector spool passagemeans, said hydraulically actuated clutches having conduit meanscommunicating with said passage means in said selector spool, wherebymodulating pressure is delivered selectively to said clutches, said highpressure fluid passage means also communicating with the side of saidpiston remote from said spring means to thereby bias said piston towardssaid valve spool to thereby bias the latter through said spring means toa position which permits an increase of pressure fluid from said highpressure fluid passage means to said modulating pressure fluid pasagemeans, the arrangement between said generally V-shaped opening on saidcontrol piston and said hole in the said selector spool is such thatwhen said selector spool is rotated in either direction from neutral,said hole is blocked until piston is shifted axially to uncover saidhole and modulating pressure fluid is directed to said engaged clutch inan amount dependent on the amount of said rotation of said selectorspool to cause clutch engagement and consequent rotation of saidpropeller shaft.
 8. The combination set forth in claim 7 furthercharacterized in that said selector spool includes a central stem withan axial passage therein and said orificing hole is located in said stemand in fluid communication with said axial passage, and furthercharacterized in that said control piston includes a sleeve in whichsaid generally V-shaped opening is located.